#### Demographic Math

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Demographic Math

Demographic math
Two things you will be able to do at
the end of this lesson:
Calculate a population’s doubling
time
Predict future population size
Please get out a calculator
Doubling time
Formula: Time =70
r
r= growth rate
Example: a country is growing at 2%
a year. In how many years will the
county’s population double?
Practice
The Ivory Coast is growing at 3.8%
each year. In how many years will it
double?
China is growing at 1.2%. In what
year will China’s population be
double what it is today?
Calculating future population
size
A = Pert
A = future population size
P = current population size
Constant e = 2.72
Growth rate r reported as percent of
percent
T = time
A = Pert
Try one!
The US population this year is 306
million and our growth rate is .6%.
How large will the population be in
2050?
Try another one!
The world’s population is about 677
million and our growth rate is 1.2%.
Assuming the rate stays constant,
how big will the population be by
2050? By 2100?
Check for understanding
What two calculations did you just
learn how to do?
What can you use A = Pert for?
Which equation is simpler?
What is the common mistake that is
made in the A = Pert formula?